1. Field of the Invention
The present invention relates to an auxiliary power system for a vehicle and, more specifically, to an auxiliary power system that includes an HVAC system.
2. Background Information
Owning to a nautical origin, a land based auxiliary power system for providing electricity to a ship while the ship is docked is identified as a “shore power system.” Shore power systems are also used to provide electrical power to land based vehicles such as trucks and recreational vehicles. Such shore power systems include both a stationary base assembly, located, for example, at a truck stop, and a vehicle assembly. The base shore power assembly and vehicle shore power assembly are coupled together to provide the vehicle with electrical power.
During normal road operation, a vehicle utilizes both electrical and mechanical energy provided by the vehicle's engine. Electrical power, created by a generator that is powered mechanically by the engine, is used to operate components such as the radio, lights, electric motors, such as the windshield wiper motors and fan motors, as well as any electrical control systems. The electrical system on a vehicle in the United States typically operates at 12V direct current. In other countries, vehicles may use a 24V direct current system. In addition to operating the generator, and providing propulsion, mechanical power is also used to cool the engine and operate the compressor for the vehicle HVAC (heating, ventilation, air conditioning) system. Also, thermal energy from the engine is used to provide heat to the HVAC system.
When the vehicle is at rest, many of the electrical systems, including recreational systems, are still used. That is, while the engine is not operating, the driver may still listen to the radio. If the electrical system is only used for a short time, electricity may be drawn from the vehicle battery. However, for extended use, such as an overnight stopover at a truckstop, the battery cannot provide sufficient power. Thus, the vehicle must be connected to a shore power system that provides electricity for components such as radios, televisions, computers, telephones and other such devices. Generally, electricity is provided at 12V DC or 24 V DC, whichever corresponds to the native current for the vehicle electrical system. However, many electrical components used in long haul trucks and recreational vehicles, such as computers and televisions, are structured to operate with an alternating current. Thus, the current must be converted to an AC current. This conversion process is very inefficient, especially if, as is typical, the electricity supplied to the shore power system is an AC current that the shore power system converts to a DC current.
During road operation, the vehicular HVAC cooling system passes a coolant fluid through the fluid loop as shown in FIG. 1. The coolant fluid is delivered to the engine compressor 62 as a low pressure gas under suction. The engine compressor 62, which is powered mechanically by the engine 3, raises the pressure, and therefore temperature, of the coolant fluid. As the coolant fluid leaves the engine compressor 62, it is a high pressure gas under positive pressure. The high pressure gas coolant fluid is passed through a condenser 66 where it is cooled. A fan, which is powered mechanically by the engine 3, enhances the air flow over the condenser 66. Because the pressure remains constant, the coolant fluid is condensed into a liquid as the temperature is lowered. The high pressure liquid coolant fluid is passed through the expansion valve 68 before entering the evaporator 70. The evaporator 70 and an evaporator fan 71 are disposed in an enclosure 34 in, or adjacent to, the vehicle cabin. As the liquid coolant fluid expands to a gas in the evaporator 70, the evaporator 70 is chilled. The evaporator fan 71 disposed adjacent to the evaporator 70 draws air over the chilled evaporator 70 and blows the cooled air into the cabin. Often, the chilled air is too cold and heat from the road HVAC heating system is added to the cabin enclosure 34 to raise the temperature of the chilled air. After the evaporator 70, the coolant fluid is again a low pressure gas under suction which is returned to the engine compressor 62.
The vehicle's HVAC compressor, which requires a considerable amount of energy to drive, is, as noted above, mechanically driven and not the vehicle's electrical system. Thus, to heat or cool the vehicle cabin, truckers typically allow the vehicle engine to idle in order for the engine to provide heat or the normal mechanical power to the compressor. This solution to providing heat or power to the condenser is very inefficient, results in high engine maintenance and creates exhaust emissions.
There is, therefore, a need for an inexpensive solution for providing temperature controlled air for a vehicle at a shore power station.
There is a further need to provide temperature controlled air for a vehicle at a shore power station that does not require extensive vehicle modification.
There is a further need to provide alternating current for a vehicle at a shore power system.